ENDOCRINE AND METABOLIC ADAPTATION FOLLOWING CESAREAN-SECTION OR VAGINAL DELIVERY

The endocrine profile (umbilical venous plasma) of three groups of inf ants was compared. Samples were taken after eight vaginal deliveries, 11 emergency caesarean sections during labour, and 13 elective caesare an sections before labour. Mean umbilical plasma concentrations of thy roxine and triiodothyronine were significantly higher and cortisol con centration were lower after elective caesarean section compared with t he two labour groups. Mean umbilical plasma thyroid stimulating hormon e (TSH) concentration was significantly lower after vaginal delivery c ompared with elective caesarean section. These results suggest that la bour reduces plasma thyroid hormone concentrations at birth in associa tion with a rise in cortisol. These adaptations may be the stimulus fo r the subsequent surge in triiodothyronine previously reported to occu r over the first few hours after birth in vaginally delivered infants.